PURPOSE: To return freezer oil which is always stable to a compressor by a method wherein two capability variable compressors connected in parallel to each other, an outdoor device provided with one accumulator and indoor devices connected in parallel to each other are provided, and each of compressor suction pipes is connected to each of two outlet pipes of the accumulator, respectively.

CONSTITUTION: In the case that a cooling is carried out only with an indoor device 15A, only a variable speed compressor 2 is operated. Refrigerant is separated from a freezer oil by an oil separator 4. Refrigerant and a partial freezer oil are circulated in a freezing cycle and returned to the compressor 2 together with gas refrigerant. The freezer oil separated from refrigerant at an oil separator 4 is mixed with refrigerant at an outlet pipe 23 of the accumulator 21 from an oil returning pipe 13 and returns to the compressor. In addition, as the indoor devices 15B and 15C are operated, a variable compressor 3 is energized. Refrigerants from both compressors are separated from the freezer oil at the oil separators 4, 5. The freezer oil not separated circulates once in the freezing cycle, is stored at a bottom part of the accumulator 21 and then it returns to both compressors with a resolving ratio between the freezer oil and refrigerant being kept at the same state.